According to a new study, even a couple of puffs of cannabis before a teen is 15 is associated with significant alterations in brain development.
Published in Journal of Neuroscience, the researchers looked at 46 teens aged 14 or younger who had smoked the equivalent of one or two joints in their lifetimes. Their brain scans were compared to 46 kids who had never used marijuana, but similar in age, IQ, socio-economic statuses, experience with alcohol, and nicotine use.
“Kids who reported just one or two (cannabis) uses in their lifetimes actually showed increased grey matter volumes in a whole bunch of brain regions,” said the study’s lead author, psychiatrist Hugh Garavan of the University of Vermont.
The larger brain volumes in those that used cannabis may be the result of less synaptic pruning, a process in which brain cells needed to soak up information in childhood are killed off in teenage years.
Past research in animals suggested a link between cannabis and brain volumes, but Garavan was still shocked.
“What made this interesting was that the brain regions affected were those areas where cannabis tends to have its effects on the brain,” he said.
The two brain regions most affected were the hippocampus, a section responsible for memory formation and spatial awareness, and the amygdala, which is involved in fear and threat processing.
Garavan adds the “pattern seen tends to be associated with lower IQs … and anxiety.”
The 2017 Ontario Student Drug Use and Health Survey asked 11,435 students in grades 7 to 12 about their drug use. Nearly one in 10 ninth graders, and one in five tenth graders, reported having used cannabis over the past 12 months.
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